Additional notes about the revision of the genus Orthocladius s. str. Van der Wulp, 1874

Palaearctic and Nearctic species belonging to the genus Orthocladius van der Wulp, 1874 were recise repeatedly (Soponis, 1977; Rossaro et al., 2003; Sæther, 2003; Spies & Sæther, 2004; Sæther, 2005). Recently the examination of the material from Goetghebuer's collection deposited at the IRSNB and from Brundin's collection deposited at the NHM allowed us to add new knowledge to this intriguing genus. An attempt to summarize the present knowledge resulted in the production of a new key to West Palaearctic species belonging to the subgenus Orthocladius s. str. known as adult males and pupal exuviae. Species belonging to the subgenus Symposiocladius Cranston and some Nearctic species, which were made available for examination, were also included in the key. The adult males can be separated on the basis of the morphology of the adult male genitalia above all, but there are species which cannot be easily separated on the basis of adult male morphology alone. The pupal exuviae often allow a better separation, but there are species whose adult males are better separated than pupal exuviae. The best situation is when both stages are available, unfortunately some species deposited at IRSNB are known only as adult males, so some questions still remain open.